In general, there is known a hybrid construction machine provided with a motor-generator that is jointed mechanically to an engine and a hydraulic pump, and an electricity storage device such as a lithium ion battery or a capacitor (for example, refer to Patent Document 1 and Patent Document 2). In this hybrid construction machine, the motor-generator plays a role of charging electric power generated by a driving force of the engine to the electricity storage device or assisting the engine by a powering operation using electric power of the electricity storage device. Many hybrid construction machines are provided with an electric motor separated from the motor-generator, and the electric motor acts for or assists in an operation of a hydraulic actuator. For example, at the time of performing a revolving movement by the electric motor, the electric motor performs or assists in the revolving movement of an upper revolving structure by electric power supply to the electric motor, and braking energy at a revolving stop is regenerated to perform a charge of the electricity storage device.
In this hydraulic construction machine, it is possible to enhance a reduction effect of a fuel consumption by increasing the output of the motor-generator or revolving electric motor. However, when the output of the motor-generator or the like is made large, there are some cases where sufficient electric power cannot be supplied due to the limitations of a discharge capability, a capacity, a temperature and the like of the electricity storage device. In this case, continuation of the electric power supply from the electricity storage device leads to hard use, accelerating degradation of the electricity storage device.
There is known the configuration made in consideration of the above problems. For example, Patent Document 1 discloses the configuration that a movement speed of a vehicle is lowered in response to a reduction of an electricity storage rate (SOC: state of charge) for preventing the degradation acceleration of the electricity storage device, preventing the hard use of the electricity storage device.
In addition, there are generally a plurality of parameters indicative of degradation of the electricity storage device, but it is difficult to simultaneously monitor the plurality of parameters. Therefore, Patent Document 2 discloses the configuration in which a plurality of parameters in regard to temperatures are mainly converted into given common scales a representative value of which is displayed on a monitor.